A turbine wastegate is type of a valve that can be controlled to selectively allow at least some exhaust to bypass a turbine. Where an exhaust turbine drives a compressor for boosting inlet pressure to an internal combustion engine (e.g., as in a turbocharger), a wastegate provides a means to control the boost pressure.
A so-called internal wastegate is integrated at least partially into a turbine housing. An internal wastegate may be configured as a type of flapper valve that includes a flapper, which may be referred to as a plug, where the plug is controllable via rotation of a shaft where an arm may extend from the shaft to the plug. The shaft can be rotatable via actuation of an actuator, which may be mechanical, electrical, etc. A mechanical linkage may operatively couple the actuator to the shaft, for example, via a shaft control arm. A plug of a wastegate often includes a flat disk shaped surface that seats against a flat seat (e.g., a valve seat or wastegate seat) disposed about an exhaust bypass opening.
In a closed position, a wastegate plug should be seated against a wastegate seat (e.g., seating surface) with sufficient force to effectively seal an exhaust bypass opening (e.g., to prevent leaking of exhaust from a high pressure exhaust supply to a lower pressure region). Often, an internal wastegate is configured to transmit force from an arm to a plug. During engine operation, load requirements for a wastegate vary with pressure differential. High load requirements can generate high mechanical stresses in a wastegate's kinematics components, a fact which has led in some instances to significantly oversized component design to meet reliability levels (e.g., as demanded by engine manufacturers). Reliability of wastegate components is a concern for diesel engine applications and for gasoline engine applications; noting that exhaust temperatures can be higher for gasoline engines. In both diesel engines and gasoline engines, exhaust pulsation can be a concern, particularly where a turbine housing receives exhaust via a plurality of passages where each passage can be dedicated to receipt of exhaust from particular combustion cylinders of an engine. Such a turbine housing can include multiple scrolls where each scroll can be dedicated to receipt of exhaust from particular combustion cylinders of an engine.
Various examples of wastegates and wastegate components are described herein, which can optionally provide for improved kinematics, reduced exhaust leakage, etc.